Molecule magic: Trapped in an Archimedean cage

As well as super-shrinking everyday gadgets such as motors, molecules have also been massaged into shapes that are more mathematical than practical.

Michael Ward of New York University and colleagues mastered a molecule-sized version of one of the 13 "Archimedean solids" – a family of symmetrical three-dimensional polyhedra attributed to the Greek mathematician.

The solid, a truncated octahedron, was built with tiny molecular tiles. One type of tile, ringed with chemical groups called guanidiniums, joined with another type ringed with sulphonates to form the shape through a connection of 72 hydrogen bonds.

The result is a hollow cage. By adding reactants to the tile mixture while cages were forming, the team also created inside them three metal "complexes" containing bismuth, lead and mercury that had never been seen before. The cage easily dissolves to release the new complexes.

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One of only 13 Archimedean solids, the truncated octahedron (Image: Scott Camazine/Alamy)